The present invention relates to an air-conditioning apparatus for heating the compartment within a vehicle with a hot water heating apparatus, and more particularly to an air conditioning apparatus that prevents window fogging due to re-evaporation of condensation water.
The present invention relates to an air-conditioning apparatus for heating the compartment within a vehicle through with a hot water heating apparatus, and more particularly to an air conditioning apparatus that prevents window fogging due to re-evaporation of condensation water.
A hot-water heating apparatus has been used to heat air with a heater core using hot-water as a heat source by circulating the hot-water (engine coolant) through the heater core during vehicle compartment heating during winter. In this case, when the hot-water temperature is low, the air outlet temperature is also low and thereby not attaining sufficient heating.
Therefore, JP-B2-5-39807 discloses a heating circuit further combined with a hot-water heating apparatus to operate a heating circuit when the air outlet temperature of the hot water heater core or hot-water temperature is lower than a predetermined temperature and to improve heating capability by heating air passing through the hot water heater core with an indoor heat exchanger and heating circuit.
In some cases, an air-conditioning mode is set to filter external air during heating in winter. In this case, the air must be cooled and dehumidified to prevent fogging. Therefore, the indoor heat exchanger is operated as an evaporator for operating the heating circuit to cool air until the external air temperature is lowered up to about 0xc2x0 C.
Therefore, in some cases, the heating circuit is operated for heating because the heating capability is reduced after the heating circuit cools to prevent fogging when the external air temperature is about 0xc2x0 C. Moreover, in some cases, the heating circuit is stopped after cooling and then started again to heat.
In the above cases, since the condensed water generated during cooling remains on the surface of the indoor heat exchanger, if the heating circuit is operated to heat, the indoor heat exchanger radiates the heat as a high pressure side heat exchanger (heat radiator of coolant gas) and thereby rapidly increasing the temperature of the indoor heat exchanger. As such, the condensed water on the surface of the indoor heat exchanger is re-evaporated and is blown into the vehicle compartment, thereby causing fogging.
Moreover, the condensed water generated during cooling with the indoor heat exchanger is not easily evaporated at the lower external air temperature during winter and thereby remains for a long time. Therefore, fogging is sometimes caused when heating begins with the heating circuit even after a certain period of time has passed after switching to cooling.
The present invention provides an air-conditioning apparatus for heating a vehicle compartment with a hot-water heating apparatus using hot-water as the heat source and using a heating circuit to defog with re-evaporation of condensed water in the indoor heat exchanger during heating circuit heating.
In one aspect of the invention, an indoor heat exchanger operates as a low pressure side heat exchanger during the heating circuit cooling and as a high pressure side heat exchanger during heating circuit heating. A heater core is positioned downstream of the indoor heat exchanger to heat the air using the hot-water as the heat source, whereby the air heating capability of the indoor heat exchanger is limited so that the temperature of indoor heat exchanger becomes lower than the first predetermined temperature during heating circuit heating.
Accordingly, the temperature of the indoor heat exchanger is maintained lower than the first predetermined temperature (Te1) during the air heating operation. Therefore, re-evaporation of the condensed water on the surface of the indoor heat exchanger can be suppressed during heating. Therefore, fogging resulting from the highly humidified air is suppressed by setting the first predetermined temperature (Te1) to a low temperature such that the condensed water is not easily re-evaporated, for instance 10xc2x0 C.
As a supply source of the hot-water to the heater core, a fuel battery or the like can be used in addition to the vehicle engine.
In another aspect, the present invention includes a determining means to determine whether the vehicle window glass is fogged or not to limit the air heating capability of the indoor heat exchanger when the determining means determines that the window glass is fogged.
Accordingly, when it is determined that the window glass is fogged during heating, the air heating capability of the indoor heat exchanger is limited to reduce blowing highly humidified air to suppress fogging. Moreover, when window glass is not fogged, this action is cancelled.
In another aspect, a determining means can determine whether fogging has occurred based on humidity near the windows as compared with general humidity. Here, humidity near the windows can be calculated (estimated) from the vehicle environment and operating conditions of the air-conditioning apparatus, in addition to the direct detection with a humidity sensor. For example, humidity of the indoor air near the window glass can be calculated (estimated) based on the physical amount in relation to the temperature of window glass. The physical amount in relation to the temperature of window glass can also be calculated (estimated) from the temperature of the window glass and some other physical quantity such as external air temperature, vehicle speed or the like correlated to the above physical amount.
Moreover, since the indoor air humidity correlates to the temperature near the window glass (when the temperature is higher, relative humidity is lower), air humidity can be estimated from the indoor air temperature near the window glass and this indoor air temperature near the window glass can be estimated from the outlet temperature of the air-conditioning apparatus.
As such, in another aspect, hot-water temperature is used as a physical amount in relation to the indoor air humidity near the window glass and it can be determined that the window glass is fogged when the hot-water temperature is lower than the predetermined hot-water temperature (Two). Namely, since the outlet temperature of the air-conditioning apparatus changes depending on the temperature of hot-water circulating in the heater core, it is determined whether the window glass is fogged or not based on the hot-water temperature.
In another aspect, the determination level (Two) of the hot-water temperature can be varied depending on the change of the external air temperature closely correlated with the temperature of the window glass and thereby fogging can be determined accurately by compensating the predetermined hot-water temperature (Two) to a higher temperature side through a drop of the external air temperature.
In another aspect, the determining means can determine whether the window glass is fogged based on the record of the heating circuit cooling.
In another aspect, the temperature of the indoor heat exchanger corresponding to an assured resistance pressure (P0) when the indoor heat exchanger operates as a low pressure side heat exchanger is set as a second predetermined temperature (Te2). Thereby, the air heating capability of the indoor heat exchanger is controlled to set the temperature of the indoor heat exchanger higher than the first predetermined temperature (Te1) but lower than the second predetermined temperature (Te2) when the determining means determines that the window glass is not fogged. As such, when the window glass is not fogged, the air heating capability of the heating circuit can be enhanced by setting the temperature of the indoor heat exchanger higher than the first predetermined temperature (Te1). Moreover, the indoor heat exchanger designed as the low pressure side heat exchanger can be preferably utilized for practical use as the high pressure side heat exchanger without any design change to improve the pressure resistance by setting the temperature of the indoor heat exchanger lower than the second predetermined temperature (Te2) corresponding to the assured resistance pressure (P0) of the heat exchanger operating as the low pressure side heat exchanger.
In another aspect, the heating circuit can be stopped when the determining means determines that the window glass is not fogged.
In another aspect, the air heating capability of the indoor heat exchanger can be controlled with a compressor of the heating circuit.
In another aspect, an indoor heat exchanger operates as a low pressure side heat exchanger during heating circuit cooling or as a high pressure side heat exchanger during the air heating operation thereof, a compressor is driven with a vehicle engine to circulate the coolant in the heating circuit and a heater core is positioned downstream of the indoor heat exchanger to heat the air using the hot-water supplied from the vehicle engine as the heat source. Thereby, power to the compressor is increased until the temperature of hot-water rises to the predetermined temperature when heating circuit heating is set.
Thereby, when the hot-water temperature is low, vehicle engine power can be increased. Therefore, rise of hot-water temperature can be accelerated. Accordingly, since the period until the hot-water temperature rises up to the predetermined temperature is shortened, vehicle compartment heating is realized quickly after the vehicle engine has started.
In another aspect, the air heating capability of the indoor heat exchanger is limited to set the temperature of the indoor heat exchanger lower than the predetermined temperature when the engine power increased.
In another aspect, since the temperature of the indoor heat exchanger is maintained under the predetermined temperature (Te1) when engine power is increased, re-evaporation of condensed water on the surface of the indoor heat exchanger can be suppressed during heating. Thereby, fogging due to blowing of highly humidified air is suppressed by setting the predetermined temperature (Te1) lower (such as, for example, 10xc2x0 C.).
Moreover, since setting the engine power to an increased condition causes the hot-water temperature to rise, the time to limit the air heating capability of the indoor heat exchanger can also be shortened to suppress fogging, helping to quickly increase the vehicle compartment heating.
In another aspect, the hot gas heater cycle that heats with exhaust gas coolant can be set by introducing the exhaust gas coolant of the compressor directly to the indoor heat exchanger and operating the hot gas heater cycle until the hot-water temperature rises to the predetermined temperature under the condition that heating circuit heating is set.
Here, in the hot gas heater cycle, the indoor heat exchanger radiates heat corresponding to the amount of compression work done by compressor. The hot gas heater cycle increases compressor power more than the heating circuit. As vehicle load of engine 22 increases, hot-water temperature rise can be accelerated and the air heating in the vehicle compartment is quickly raised by selecting the hot gas heater cycle when the hot-water temperature is low.
In another aspect, an electric expansion valve is provided to reduce high pressure coolant passing to the indoor heat exchanger to a low pressure coolant during heating circuit heating. As such, an opening angle of the electric expansion valve can be held in the predetermined opening angle or more until the hot-water temperature rises to the predetermined temperature during heating circuit heating.
Thereby, since compressor 11 power can be increased with increased coolant circulation of the heating circuit 10 by increasing the opening angle of the electric expansion valve when the hot-water temperature is low, engine 22 power is increased to increase the hot-water temperature and thereby increase vehicle compartment heating.
In another aspect, high pressure (high pressure coolant temperature) during heating can further be increased by utilizing CO2 as the coolant.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.